When you get "Could not update video settings. Please try again later" or "Failed to publish video" or simply even if you manually click "Publish" it fails to publish the video, the problem is caused by a YouTube security measure.

Because you are uploading too fast, YouTube will block you for a certain period of time. What you need to do is this: a) Use big delays. 100-120 seconds between uploads b) Use proxies (if a fails) c) Wait a bit (5-8 hours) until YouTube unblocks uploading for your account